This property hasn't actually done anything for a long time. We should remove it and not look back.
Created attachment 148349 [details] Seriously exciting patch
Committed r120735: <http://trac.webkit.org/changeset/120735>
(In reply to comment #2) > Committed r120735: <http://trac.webkit.org/changeset/120735> And expected update landed in http://trac.webkit.org/changeset/120800